From 730dc6b98569c072aaee9324e58e790973690d2d Mon Sep 17 00:00:00 2001
From: Ben Schumacher <ben.schumacher@mattermost.com>
Date: Mon, 19 Apr 2021 14:02:00 +0200
Subject: [PATCH] [MM-34919] Use Mattermost-Plugin-ID header to pass ID in
 inter-plugin requests (#17418)

---
 app/plugin_api_test.go | 4 ++++
 app/plugin_requests.go | 5 +++++
 plugin/context.go      | 2 +-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/app/plugin_api_test.go b/app/plugin_api_test.go
index 5dfdb68002..70bf95b230 100644
--- a/app/plugin_api_test.go
+++ b/app/plugin_api_test.go
@@ -1404,6 +1404,10 @@ func TestInterpluginPluginHTTP(t *testing.T) {
 				return
 			}
 
+			if r.Header.Get("Mattermost-Plugin-ID") != "testplugininterclient" {
+				return
+			}
+
 			buf := bytes.Buffer{}
 			buf.ReadFrom(r.Body)
 			resp := "we got:" + buf.String()
diff --git a/app/plugin_requests.go b/app/plugin_requests.go
index 67775c5309..d0132fcb72 100644
--- a/app/plugin_requests.go
+++ b/app/plugin_requests.go
@@ -74,6 +74,8 @@ func (a *App) ServeInterPluginRequest(w http.ResponseWriter, r *http.Request, so
 		SourcePluginId: sourcePluginId,
 	}
 
+	r.Header.Set("Mattermost-Plugin-ID", sourcePluginId)
+
 	hooks.ServeHTTP(context, w, r)
 }
 
@@ -135,6 +137,9 @@ func (a *App) servePluginRequest(w http.ResponseWriter, r *http.Request, handler
 		token = r.URL.Query().Get("access_token")
 	}
 
+	// Mattermost-Plugin-ID can only be set by inter-plugin requests
+	r.Header.Del("Mattermost-Plugin-ID")
+
 	r.Header.Del("Mattermost-User-Id")
 	if token != "" {
 		session, err := a.GetSession(token)
diff --git a/plugin/context.go b/plugin/context.go
index 98e786e8c5..d8fa94f645 100644
--- a/plugin/context.go
+++ b/plugin/context.go
@@ -12,5 +12,5 @@ type Context struct {
 	IpAddress      string
 	AcceptLanguage string
 	UserAgent      string
-	SourcePluginId string
+	SourcePluginId string // Deprecated: Use the "Mattermost-Plugin-ID" HTTP header instead
 }